I have a Ubuntu 12.04 PC that sometimes does not detect my Samsung Galaxy Note 2 smartphone. The following error message will pop up when I connect the device.
Unable to mount SAMSUNG_Android Unable to open MTP device '[usb:001, 085]'
USB debugging has been enabled on the device, and 51-android.rules/52-android.rules both have the device USB PID in them.
adb detects my Galaxy S3 and Nexus 5 just fine.
I've tried rebooting the phone, as well as killing-restarting adb, but still nothing.